DTMF digits are ignored by an IVR

Describe the digit failure

Record whether the menu misses all digits, misses some, doubles digits or fails only after transfer. Compare the handset's local key tone with the remote menu response; local sound is not evidence of successful signaling to the IVR.

Inspect the negotiated method

Check whether the endpoints use in-band audio, RTP telephone events or a supported signaling method. For RTP events, inspect the SDP mapping and accepted event capabilities on the affected leg. Do not impose a fixed dynamic payload number copied from another system.

A PBX can use different methods on each leg. An internal IVR working does not prove the carrier-facing event negotiation is correct.

Reproduce a bounded test

Enter single, repeated and different digits slowly on a known authorized test menu. Compare another endpoint and route. If the problem appears only after hold or transfer, inspect the later negotiation.

Make the compatible change

Align the mismatched endpoints with their official settings and repeat the exact sequence. Avoid enabling multiple methods indiscriminately, because duplicated representations can produce double input. Use the DTMF protocol guide to understand the negotiated fields before changing codecs.